Rapid Prototyping

Egyre gyakrabban beszélünk a virtuális termékfejlesztésről, ahol a termék csak a számítógép monitorán jelenik meg, de sokszor elkerülhetetlen a kézbefogható, kipróbálható és tesztelhető modell(ek) elkészítése a sorozatgyártás megkezdése előtt.
Ezeknek a prototípusoknak az elkészítéséhez a CADworks Kft. -a Modell Technik Rapid Prototyping GmbH. képviselőjeként- az alábbiakban ismertetett gyors prototípusgyártási technológiákat tudja felajánlani Önöknek. A gyors prototípusgyártáshoz 3D-s CAD modell szükséges. Ha Önöknek csak 2D-s rajza vagy csak formai elképzelései vannak, akkor mi elkészítjük a 3D-s CAD modellt is. Egy szoftver segítségével a CAD modellt felszeleteljük és az így készített rétegekből a gyors prototípust gyártó gép előállítja az alkatrészt. Ebből az alkatrészből könnyen lehet öntő- illetve fröccsszerszámot készíteni.

Stereolithography - SLA

Stereolithography is the oldest and widest spread Rapid Prototyping process. During the building process a physical model is generated layer by layer from a viscous resin. The build platform is placed in a vat filled with liquid monomers. This resin cures through photopolymerisation set off by UV. During the process a UV laser scans the outline of the part to build. The thickness of the cured layer is limited to some decimillimeters according to the total light energy absorbed by the resin. After the solidification of a layer the build platform moves down, making room for the re-coating of the layer with liquid resin. To achieve a smooth surface of the liquid resin a scraper blade sweeps over it. After this process a new layer can be built up.
  • at present the most accurate Rapid Prototyping process
  • high complexity possible
  • hollow spaces possible
  • Complex parts as design patterns or patterns for form and fit analysis
SLA

Selective Laser-Sintering - SLS

Local melting of an initially powdered material by means of a CO2-Laser.
SLS

Fused Deposition Modelling - FDM

Fused Deposition Modeling is a process, in which filamentary material is lead trough a temperature-controlled extrusion head, which operates in the x-y-plane. The melted material is extruded and laid down layer by layer on a building platform according to a given outline. The building platform moves in z-axis direction. After each layer the platform moves down over the required layer thickness. Then the machine generates the next layer, which fuses with the part already built. Fused Deposition Modelling is suitable for low melting materials of low thermal conductivity. ABS is a material of high strength.
  • simple operating technology
  • no laser necessary
  • no waste of material
  • no special requirements concerning the machine
  • voluminous parts with tick walls
  • functional prototypes
  • parts with low requirements on surface finish
FDM

Laminated Object Manufacturing - LOM

A modell papírrétegek egymásra ragasztásával jön létre. A kész darab nagymértékben hasonlít a keményfából készült modellekhez.
  • Vizuális és funkcionális modell.
  • Jó felületi minőség érhető el csiszolással és lakkozással.
  • Az itt kapott alkatrész a vákuum-öntés, centrifugál-öntés és precíziós öntés alapjaként szolgál.
  • Az így előállított alkatrészek ragaszthatók, polírozhatók, lakkozhatók.
  • Az alkatrészek kevéssé terhelhetők.
 

Spin-Casting

Spin Casting is a duplication process for metal parts from high strength zinc-alloy. The necessary master pattern may be manufactured traditionally or generated in a Rapid Prototyping process as Stereolithography and Selective-Laser-Sintering of metal. For the tool production a master pattern is necessary, which has to be previously prepared for the casting process by adding a calculated shrinkage factor. The tool is made from a putty-like modelling clay, in which are placed number of masters, distributed around the molds center. The mold cures by vulcanising it. After its solidification the master can be removed and the rubber-like mold gated and vented. Spin-casting tools are always circular, because during the casting process the mold rotates at high speed around the mold's lug, thus using the centrifugal force to fill the tool. After their solidification the cast parts may be removed from the mold. Draft angles need not to be taken into account, undercuts are carried out by means of separate parts, high complexity is reached by means of special inserts.
  • Rapid manufacturing of small metal parts
  • small and medium series possible
  • Only limited part size and complexity possible
  • Best possible accuracy +/- 0,2% tolerances to nominal values, minimum 0,2mm
  • only possible material: zinc alloy, because of its low melting point
  • higher weight than aluminium
  • Metal parts from zinc alloy of low complexity
  • small and medium series

Vacuum Casting

Vacuum Casting is the most frequently employed duplication process following the SLA process. The vacuum casting mold is a silicon tool used for the production of plastic parts. The master pattern may be generated through Stereolithography or manufactured traditionally. Once the sprue and the parting line of the tool are defined, the model is placed in the mold chase and backfilled with a special liquid silicone. After solidification of the silicone mold, it can be separated along the parting line and the master model removed. The next step of the process consists in evacuating the mold and filling it in a vacuum with a special bi-component plastic.
  • low cost process
  • Various materials with different properties approaching mass production requirements
  • undercuts possible
  • Draft angles need not to be considered
  • small number of parts
  • Slightly reduced accuracy as a result of the flexibility of the tool no casting of series materials possible
  • Small numbers of filigree and complex models

Quick Cast

The term Quick Cast refers to a special building method in Stereolithography, which is capable of generating "lost patterns" for investment casting. These patterns have a solid outer skin but a hollow honeycomb internal structure. Therefore they are very light. It is also possible to use other Rapid Prototyping processes to generate masters for investment casting, such as · polystyrole patterns waxed · polycarbonate patterns waxed · wax patterns This master is repeatedly dipped into a special ceramic slurry, consisting of fire resistant molding sands and binders. By showering sand over the model and drying it, a thick ceramic shell of several tightly bound layers is built up. Next, the core with the ceramic shell is padded with sand and the master pattern extracted from the shell by heating the assembly. The empty shell is then densified by further heating, in order to obtain a shell that tolerates the metal casting. The molten metal is cast into the hot shell. After the cooling of the cast parts the ceramic shell is destroyed and gates removed. As this process relies on "lost models", a new master pattern is necessary for each part.
  • good surface quality possible
  • very good structure
  • high accuracy
  • precise duplication of the master
  • time-consuming process
  • several masters necessary
  • small numbers of investment cast parts
  • very precise and strong prototypes
 

Rapid Tooling - Direct Laser Sintering of Metal

Direct laser sintering of metal powder is a process that - like the already described selective laser sintering of plastics - generates a part layer by layer on a build platform. The STL-data necessary for the building process are derived from a 3D/CAD - model. Ac-cording to the information about each layer the part is built up in a powder bed. Through a special lens the CO2 laser beam is focused on the powder bed surface. After the scanning of each layer the build platform lowers over one layer 'thickness - typically 0,1 mm. Simul-taneously the powder reservoir moves up, and an amount of powder is put in front of the blade, which sweeps over the build platform. The question whether the process can be employed or not largely depends on the available powder alloys, which must allow a selective sintering without yielding warpage, bowing or curling. Usable are three phase powders consisting of a low- and a high melting phase. Similar to the liquid phase sintering the low melting phase melts on absorption of the laser energy and fuses with the high-melting phase. The latter does not melt but expands through an irreversible crystal lattice transformation, which prevents shrinkage and allows high ac-curacy of the part. A further advantage of this material is, that it can be treated at room tem-perature without complex process devices as special process chamber heatings or supple-mentary powder compaction devices.
  • short building times
  • no time-consuming cooling process
  • good accuracy
  • grainy structure needs infiltration with epoxy resin
  • post-procedural erosion possible only to a limited extent
  • inserts for injection molding

Rapid Tooling - Indirect Laser Sintering of Metal

The SLS feedstock powder is a low-carbon steel-shot material with an average particle size of 50µm, coated with a 5µm polymer. In the SLS process, a laser is used to selectively melt the polymer coating. The resulting "green part" has low mechanical strength and density. It is post-processed by soaking it in a dilute aqueous polymer binder. When placed into a 5mm deep bath, up to 100mm high "green parts" can be infiltrated in as short as half an hour. The saturated parts are then dried at approximately 50°C in a laboratory oven until complete drying, in order to avoid that bubbles emerge during the following oven-process. The last step of this process is a furnace cycle, which has great influence on the part's accuracy. First the part must be weighed in order to determine the necessary amount of copper to infiltrate the part. The green part is then placed in a graphite crucible with blocks of copper. The furnace cycle consists of several steps. The polymer removal step occurs at 350 - 450°C. The sample is then heated to a temperature of 1,050°C. At this temperature the steel powder begins to sinter and the particles are bound together by surface friction. As the steel powder does not completely melt, the porosity degree remains high. The part is 60% steel at that moment of the process. Next, the steel skeleton is infiltrated with copper at a temperature of 1,120°C. Infiltration is driven by capillary forces . This step of the process has great influence on the shrinkage of the part. At the present state-of-the art it is at about 4.3%. After cooling to room temperature, the tool can be removed from the oven. It is now 60% steel and 40% copper.
  • full-metal parts
  • high technical and mechanical strength of the parts
  • unlimited post-procedural machining possible
  • time consuming process
  • time consuming cooling period
  • shrinkage due to thermal treatment
  • inserts for injection molding and die casting